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rpmsg: char: Add lock to avoid race when rpmsg device is released

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When remote host goes down glink char device channel is freed and
associated rpdev is destroyed through rpmsg_chrdev_eptdev_destroy(),
At the same time user space apps can still try to open/poll rpmsg
char device which will result in calling rpmsg_create_ept()/rpmsg_poll().
These functions will try to reference rpdev which has already been freed
through rpmsg_chrdev_eptdev_destroy().

File operation functions and device removal function must be protected
with lock. This patch adds existing ept lock in remove function as well.

Signed-off-by: Deepak Kumar Singh <quic_deesin@quicinc.com>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/1663584840-15762-2-git-send-email-quic_deesin@quicinc.com
This commit is contained in:
Deepak Kumar Singh 2022-09-19 16:23:59 +05:30 committed by Bjorn Andersson
parent d2ff0f84c1
commit 17b88a2050
1 changed files with 8 additions and 0 deletions
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8
drivers/rpmsg/rpmsg_char.c
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@ -75,6 +75,7 @@ int rpmsg_chrdev_eptdev_destroy(struct device *dev, void *data)
struct rpmsg_eptdev *eptdev = dev_to_eptdev(dev);
mutex_lock(&eptdev->ept_lock);
eptdev->rpdev = NULL;
if (eptdev->ept) {
/* The default endpoint is released by the rpmsg core */
if (!eptdev->default_ept)
@ -128,6 +129,11 @@ static int rpmsg_eptdev_open(struct inode *inode, struct file *filp)
return -EBUSY;
}
if (!eptdev->rpdev) {
mutex_unlock(&eptdev->ept_lock);
return -ENETRESET;
}
get_device(dev);
/*
@ -279,7 +285,9 @@ static __poll_t rpmsg_eptdev_poll(struct file *filp, poll_table *wait)
if (!skb_queue_empty(&eptdev->queue))
mask |= EPOLLIN | EPOLLRDNORM;
mutex_lock(&eptdev->ept_lock);
mask |= rpmsg_poll(eptdev->ept, filp, wait);
mutex_unlock(&eptdev->ept_lock);
return mask;
}